Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]
FreeBSD/Linux Kernel Cross Reference
sys/kern/link_elf.c
Version:
- FREEBSD - FREEBSD-13-STABLE - FREEBSD-13-0 - FREEBSD-12-STABLE - FREEBSD-12-0 - FREEBSD-11-STABLE - FREEBSD-11-0 - FREEBSD-10-STABLE - FREEBSD-10-0 - FREEBSD-9-STABLE - FREEBSD-9-0 - FREEBSD-8-STABLE - FREEBSD-8-0 - FREEBSD-7-STABLE - FREEBSD-7-0 - FREEBSD-6-STABLE - FREEBSD-6-0 - FREEBSD-5-STABLE - FREEBSD-5-0 - FREEBSD-4-STABLE - FREEBSD-3-STABLE - FREEBSD22 - l41 - OPENBSD - linux-2.6 - MK84 - PLAN9 - xnu-8792
SearchContext: - none - 3 - 10
SearchContext: - none - 3 - 10
1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 3 * 4 * Copyright (c) 1998-2000 Doug Rabson 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #include <sys/cdefs.h> 30 __FBSDID("$FreeBSD$"); 31 32 #include "opt_ddb.h" 33 #include "opt_gdb.h" 34 35 #include <sys/param.h> 36 #include <sys/systm.h> 37 #ifdef GPROF 38 #include <sys/gmon.h> 39 #endif 40 #include <sys/kernel.h> 41 #include <sys/lock.h> 42 #include <sys/malloc.h> 43 #ifdef SPARSE_MAPPING 44 #include <sys/mman.h> 45 #endif 46 #include <sys/mutex.h> 47 #include <sys/mount.h> 48 #include <sys/pcpu.h> 49 #include <sys/proc.h> 50 #include <sys/namei.h> 51 #include <sys/fcntl.h> 52 #include <sys/vnode.h> 53 #include <sys/linker.h> 54 #include <sys/sysctl.h> 55 56 #include <machine/elf.h> 57 58 #include <net/vnet.h> 59 60 #include <security/mac/mac_framework.h> 61 62 #include <vm/vm.h> 63 #include <vm/vm_param.h> 64 #ifdef SPARSE_MAPPING 65 #include <vm/vm_object.h> 66 #include <vm/vm_kern.h> 67 #include <vm/vm_extern.h> 68 #endif 69 #include <vm/pmap.h> 70 #include <vm/vm_map.h> 71 72 #include <sys/link_elf.h> 73 74 #include "linker_if.h" 75 76 #define MAXSEGS 4 77 78 typedef struct elf_file { 79 struct linker_file lf; /* Common fields */ 80 int preloaded; /* Was file pre-loaded */ 81 caddr_t address; /* Relocation address */ 82 #ifdef SPARSE_MAPPING 83 vm_object_t object; /* VM object to hold file pages */ 84 #endif 85 Elf_Dyn *dynamic; /* Symbol table etc. */ 86 Elf_Hashelt nbuckets; /* DT_HASH info */ 87 Elf_Hashelt nchains; 88 const Elf_Hashelt *buckets; 89 const Elf_Hashelt *chains; 90 caddr_t hash; 91 caddr_t strtab; /* DT_STRTAB */ 92 int strsz; /* DT_STRSZ */ 93 const Elf_Sym *symtab; /* DT_SYMTAB */ 94 Elf_Addr *got; /* DT_PLTGOT */ 95 const Elf_Rel *pltrel; /* DT_JMPREL */ 96 int pltrelsize; /* DT_PLTRELSZ */ 97 const Elf_Rela *pltrela; /* DT_JMPREL */ 98 int pltrelasize; /* DT_PLTRELSZ */ 99 const Elf_Rel *rel; /* DT_REL */ 100 int relsize; /* DT_RELSZ */ 101 const Elf_Rela *rela; /* DT_RELA */ 102 int relasize; /* DT_RELASZ */ 103 caddr_t modptr; 104 const Elf_Sym *ddbsymtab; /* The symbol table we are using */ 105 long ddbsymcnt; /* Number of symbols */ 106 caddr_t ddbstrtab; /* String table */ 107 long ddbstrcnt; /* number of bytes in string table */ 108 caddr_t symbase; /* malloc'ed symbold base */ 109 caddr_t strbase; /* malloc'ed string base */ 110 caddr_t ctftab; /* CTF table */ 111 long ctfcnt; /* number of bytes in CTF table */ 112 caddr_t ctfoff; /* CTF offset table */ 113 caddr_t typoff; /* Type offset table */ 114 long typlen; /* Number of type entries. */ 115 Elf_Addr pcpu_start; /* Pre-relocation pcpu set start. */ 116 Elf_Addr pcpu_stop; /* Pre-relocation pcpu set stop. */ 117 Elf_Addr pcpu_base; /* Relocated pcpu set address. */ 118 #ifdef VIMAGE 119 Elf_Addr vnet_start; /* Pre-relocation vnet set start. */ 120 Elf_Addr vnet_stop; /* Pre-relocation vnet set stop. */ 121 Elf_Addr vnet_base; /* Relocated vnet set address. */ 122 #endif 123 #ifdef GDB 124 struct link_map gdb; /* hooks for gdb */ 125 #endif 126 } *elf_file_t; 127 128 struct elf_set { 129 Elf_Addr es_start; 130 Elf_Addr es_stop; 131 Elf_Addr es_base; 132 TAILQ_ENTRY(elf_set) es_link; 133 }; 134 135 TAILQ_HEAD(elf_set_head, elf_set); 136 137 #include <kern/kern_ctf.c> 138 139 static int link_elf_link_common_finish(linker_file_t); 140 static int link_elf_link_preload(linker_class_t cls, 141 const char *, linker_file_t *); 142 static int link_elf_link_preload_finish(linker_file_t); 143 static int link_elf_load_file(linker_class_t, const char *, 144 linker_file_t *); 145 static int link_elf_lookup_symbol(linker_file_t, const char *, 146 c_linker_sym_t *); 147 static int link_elf_symbol_values(linker_file_t, c_linker_sym_t, 148 linker_symval_t *); 149 static int link_elf_search_symbol(linker_file_t, caddr_t, 150 c_linker_sym_t *, long *); 151 152 static void link_elf_unload_file(linker_file_t); 153 static void link_elf_unload_preload(linker_file_t); 154 static int link_elf_lookup_set(linker_file_t, const char *, 155 void ***, void ***, int *); 156 static int link_elf_each_function_name(linker_file_t, 157 int (*)(const char *, void *), void *); 158 static int link_elf_each_function_nameval(linker_file_t, 159 linker_function_nameval_callback_t, void *); 160 static void link_elf_reloc_local(linker_file_t); 161 static long link_elf_symtab_get(linker_file_t, const Elf_Sym **); 162 static long link_elf_strtab_get(linker_file_t, caddr_t *); 163 static int elf_lookup(linker_file_t, Elf_Size, int, Elf_Addr *); 164 165 static kobj_method_t link_elf_methods[] = { 166 KOBJMETHOD(linker_lookup_symbol, link_elf_lookup_symbol), 167 KOBJMETHOD(linker_symbol_values, link_elf_symbol_values), 168 KOBJMETHOD(linker_search_symbol, link_elf_search_symbol), 169 KOBJMETHOD(linker_unload, link_elf_unload_file), 170 KOBJMETHOD(linker_load_file, link_elf_load_file), 171 KOBJMETHOD(linker_link_preload, link_elf_link_preload), 172 KOBJMETHOD(linker_link_preload_finish, link_elf_link_preload_finish), 173 KOBJMETHOD(linker_lookup_set, link_elf_lookup_set), 174 KOBJMETHOD(linker_each_function_name, link_elf_each_function_name), 175 KOBJMETHOD(linker_each_function_nameval, link_elf_each_function_nameval), 176 KOBJMETHOD(linker_ctf_get, link_elf_ctf_get), 177 KOBJMETHOD(linker_symtab_get, link_elf_symtab_get), 178 KOBJMETHOD(linker_strtab_get, link_elf_strtab_get), 179 KOBJMETHOD_END 180 }; 181 182 static struct linker_class link_elf_class = { 183 #if ELF_TARG_CLASS == ELFCLASS32 184 "elf32", 185 #else 186 "elf64", 187 #endif 188 link_elf_methods, sizeof(struct elf_file) 189 }; 190 191 typedef int (*elf_reloc_fn)(linker_file_t lf, Elf_Addr relocbase, 192 const void *data, int type, elf_lookup_fn lookup); 193 194 static int parse_dynamic(elf_file_t); 195 static int relocate_file(elf_file_t); 196 static int relocate_file1(elf_file_t ef, elf_lookup_fn lookup, 197 elf_reloc_fn reloc, bool ifuncs); 198 static int link_elf_preload_parse_symbols(elf_file_t); 199 200 static struct elf_set_head set_pcpu_list; 201 #ifdef VIMAGE 202 static struct elf_set_head set_vnet_list; 203 #endif 204 205 static void 206 elf_set_add(struct elf_set_head *list, Elf_Addr start, Elf_Addr stop, Elf_Addr base) 207 { 208 struct elf_set *set, *iter; 209 210 set = malloc(sizeof(*set), M_LINKER, M_WAITOK); 211 set->es_start = start; 212 set->es_stop = stop; 213 set->es_base = base; 214 215 TAILQ_FOREACH(iter, list, es_link) { 216 KASSERT((set->es_start < iter->es_start && set->es_stop < iter->es_stop) || 217 (set->es_start > iter->es_start && set->es_stop > iter->es_stop), 218 ("linker sets intersection: to insert: 0x%jx-0x%jx; inserted: 0x%jx-0x%jx", 219 (uintmax_t)set->es_start, (uintmax_t)set->es_stop, 220 (uintmax_t)iter->es_start, (uintmax_t)iter->es_stop)); 221 222 if (iter->es_start > set->es_start) { 223 TAILQ_INSERT_BEFORE(iter, set, es_link); 224 break; 225 } 226 } 227 228 if (iter == NULL) 229 TAILQ_INSERT_TAIL(list, set, es_link); 230 } 231 232 static int 233 elf_set_find(struct elf_set_head *list, Elf_Addr addr, Elf_Addr *start, Elf_Addr *base) 234 { 235 struct elf_set *set; 236 237 TAILQ_FOREACH(set, list, es_link) { 238 if (addr < set->es_start) 239 return (0); 240 if (addr < set->es_stop) { 241 *start = set->es_start; 242 *base = set->es_base; 243 return (1); 244 } 245 } 246 247 return (0); 248 } 249 250 static void 251 elf_set_delete(struct elf_set_head *list, Elf_Addr start) 252 { 253 struct elf_set *set; 254 255 TAILQ_FOREACH(set, list, es_link) { 256 if (start < set->es_start) 257 break; 258 if (start == set->es_start) { 259 TAILQ_REMOVE(list, set, es_link); 260 free(set, M_LINKER); 261 return; 262 } 263 } 264 KASSERT(0, ("deleting unknown linker set (start = 0x%jx)", 265 (uintmax_t)start)); 266 } 267 268 #ifdef GDB 269 static void r_debug_state(struct r_debug *, struct link_map *); 270 271 /* 272 * A list of loaded modules for GDB to use for loading symbols. 273 */ 274 struct r_debug r_debug; 275 276 #define GDB_STATE(s) do { \ 277 r_debug.r_state = s; r_debug_state(NULL, NULL); \ 278 } while (0) 279 280 /* 281 * Function for the debugger to set a breakpoint on to gain control. 282 */ 283 static void 284 r_debug_state(struct r_debug *dummy_one __unused, 285 struct link_map *dummy_two __unused) 286 { 287 } 288 289 static void 290 link_elf_add_gdb(struct link_map *l) 291 { 292 struct link_map *prev; 293 294 l->l_next = NULL; 295 296 if (r_debug.r_map == NULL) { 297 /* Add first. */ 298 l->l_prev = NULL; 299 r_debug.r_map = l; 300 } else { 301 /* Append to list. */ 302 for (prev = r_debug.r_map; 303 prev->l_next != NULL; 304 prev = prev->l_next) 305 ; 306 l->l_prev = prev; 307 prev->l_next = l; 308 } 309 } 310 311 static void 312 link_elf_delete_gdb(struct link_map *l) 313 { 314 if (l->l_prev == NULL) { 315 /* Remove first. */ 316 if ((r_debug.r_map = l->l_next) != NULL) 317 l->l_next->l_prev = NULL; 318 } else { 319 /* Remove any but first. */ 320 if ((l->l_prev->l_next = l->l_next) != NULL) 321 l->l_next->l_prev = l->l_prev; 322 } 323 } 324 #endif /* GDB */ 325 326 /* 327 * The kernel symbol table starts here. 328 */ 329 extern struct _dynamic _DYNAMIC; 330 331 static void 332 link_elf_error(const char *filename, const char *s) 333 { 334 if (filename == NULL) 335 printf("kldload: %s\n", s); 336 else 337 printf("kldload: %s: %s\n", filename, s); 338 } 339 340 static void 341 link_elf_invoke_ctors(caddr_t addr, size_t size) 342 { 343 void (**ctor)(void); 344 size_t i, cnt; 345 346 if (addr == NULL || size == 0) 347 return; 348 cnt = size / sizeof(*ctor); 349 ctor = (void *)addr; 350 for (i = 0; i < cnt; i++) { 351 if (ctor[i] != NULL) 352 (*ctor[i])(); 353 } 354 } 355 356 /* 357 * Actions performed after linking/loading both the preloaded kernel and any 358 * modules; whether preloaded or dynamicly loaded. 359 */ 360 static int 361 link_elf_link_common_finish(linker_file_t lf) 362 { 363 #ifdef GDB 364 elf_file_t ef = (elf_file_t)lf; 365 char *newfilename; 366 #endif 367 int error; 368 369 /* Notify MD code that a module is being loaded. */ 370 error = elf_cpu_load_file(lf); 371 if (error != 0) 372 return (error); 373 374 #ifdef GDB 375 GDB_STATE(RT_ADD); 376 ef->gdb.l_addr = lf->address; 377 newfilename = malloc(strlen(lf->filename) + 1, M_LINKER, M_WAITOK); 378 strcpy(newfilename, lf->filename); 379 ef->gdb.l_name = newfilename; 380 ef->gdb.l_ld = ef->dynamic; 381 link_elf_add_gdb(&ef->gdb); 382 GDB_STATE(RT_CONSISTENT); 383 #endif 384 385 /* Invoke .ctors */ 386 link_elf_invoke_ctors(lf->ctors_addr, lf->ctors_size); 387 return (0); 388 } 389 390 #ifdef RELOCATABLE_KERNEL 391 /* 392 * __startkernel and __endkernel are symbols set up as relocation canaries. 393 * 394 * They are defined in locore to reference linker script symbols at the 395 * beginning and end of the LOAD area. This has the desired side effect of 396 * giving us variables that have relative relocations pointing at them, so 397 * relocation of the kernel object will cause the variables to be updated 398 * automatically by the runtime linker when we initialize. 399 * 400 * There are two main reasons to relocate the kernel: 401 * 1) If the loader needed to load the kernel at an alternate load address. 402 * 2) If the kernel is switching address spaces on machines like POWER9 403 * under Radix where the high bits of the effective address are used to 404 * differentiate between hypervisor, host, guest, and problem state. 405 */ 406 extern vm_offset_t __startkernel, __endkernel; 407 #endif 408 409 static unsigned long kern_relbase = KERNBASE; 410 411 SYSCTL_ULONG(_kern, OID_AUTO, base_address, CTLFLAG_RD, 412 SYSCTL_NULL_ULONG_PTR, KERNBASE, "Kernel base address"); 413 SYSCTL_ULONG(_kern, OID_AUTO, relbase_address, CTLFLAG_RD, 414 &kern_relbase, 0, "Kernel relocated base address"); 415 416 static void 417 link_elf_init(void* arg) 418 { 419 Elf_Dyn *dp; 420 Elf_Addr *ctors_addrp; 421 Elf_Size *ctors_sizep; 422 caddr_t modptr, baseptr, sizeptr; 423 elf_file_t ef; 424 const char *modname; 425 426 linker_add_class(&link_elf_class); 427 428 dp = (Elf_Dyn *)&_DYNAMIC; 429 modname = NULL; 430 modptr = preload_search_by_type("elf" __XSTRING(__ELF_WORD_SIZE) " kernel"); 431 if (modptr == NULL) 432 modptr = preload_search_by_type("elf kernel"); 433 modname = (char *)preload_search_info(modptr, MODINFO_NAME); 434 if (modname == NULL) 435 modname = "kernel"; 436 linker_kernel_file = linker_make_file(modname, &link_elf_class); 437 if (linker_kernel_file == NULL) 438 panic("%s: Can't create linker structures for kernel", 439 __func__); 440 441 ef = (elf_file_t) linker_kernel_file; 442 ef->preloaded = 1; 443 #ifdef RELOCATABLE_KERNEL 444 /* Compute relative displacement */ 445 ef->address = (caddr_t) (__startkernel - KERNBASE); 446 #else 447 ef->address = 0; 448 #endif 449 #ifdef SPARSE_MAPPING 450 ef->object = NULL; 451 #endif 452 ef->dynamic = dp; 453 454 if (dp != NULL) 455 parse_dynamic(ef); 456 #ifdef RELOCATABLE_KERNEL 457 linker_kernel_file->address = (caddr_t)__startkernel; 458 linker_kernel_file->size = (intptr_t)(__endkernel - __startkernel); 459 kern_relbase = (unsigned long)__startkernel; 460 #else 461 linker_kernel_file->address += KERNBASE; 462 linker_kernel_file->size = -(intptr_t)linker_kernel_file->address; 463 #endif 464 465 if (modptr != NULL) { 466 ef->modptr = modptr; 467 baseptr = preload_search_info(modptr, MODINFO_ADDR); 468 if (baseptr != NULL) 469 linker_kernel_file->address = *(caddr_t *)baseptr; 470 sizeptr = preload_search_info(modptr, MODINFO_SIZE); 471 if (sizeptr != NULL) 472 linker_kernel_file->size = *(size_t *)sizeptr; 473 ctors_addrp = (Elf_Addr *)preload_search_info(modptr, 474 MODINFO_METADATA | MODINFOMD_CTORS_ADDR); 475 ctors_sizep = (Elf_Size *)preload_search_info(modptr, 476 MODINFO_METADATA | MODINFOMD_CTORS_SIZE); 477 if (ctors_addrp != NULL && ctors_sizep != NULL) { 478 linker_kernel_file->ctors_addr = ef->address + 479 *ctors_addrp; 480 linker_kernel_file->ctors_size = *ctors_sizep; 481 } 482 } 483 (void)link_elf_preload_parse_symbols(ef); 484 485 #ifdef GDB 486 r_debug.r_map = NULL; 487 r_debug.r_brk = r_debug_state; 488 r_debug.r_state = RT_CONSISTENT; 489 #endif 490 491 (void)link_elf_link_common_finish(linker_kernel_file); 492 linker_kernel_file->flags |= LINKER_FILE_LINKED; 493 TAILQ_INIT(&set_pcpu_list); 494 #ifdef VIMAGE 495 TAILQ_INIT(&set_vnet_list); 496 #endif 497 } 498 499 SYSINIT(link_elf, SI_SUB_KLD, SI_ORDER_THIRD, link_elf_init, NULL); 500 501 static int 502 link_elf_preload_parse_symbols(elf_file_t ef) 503 { 504 caddr_t pointer; 505 caddr_t ssym, esym, base; 506 caddr_t strtab; 507 int strcnt; 508 Elf_Sym *symtab; 509 int symcnt; 510 511 if (ef->modptr == NULL) 512 return (0); 513 pointer = preload_search_info(ef->modptr, 514 MODINFO_METADATA | MODINFOMD_SSYM); 515 if (pointer == NULL) 516 return (0); 517 ssym = *(caddr_t *)pointer; 518 pointer = preload_search_info(ef->modptr, 519 MODINFO_METADATA | MODINFOMD_ESYM); 520 if (pointer == NULL) 521 return (0); 522 esym = *(caddr_t *)pointer; 523 524 base = ssym; 525 526 symcnt = *(long *)base; 527 base += sizeof(long); 528 symtab = (Elf_Sym *)base; 529 base += roundup(symcnt, sizeof(long)); 530 531 if (base > esym || base < ssym) { 532 printf("Symbols are corrupt!\n"); 533 return (EINVAL); 534 } 535 536 strcnt = *(long *)base; 537 base += sizeof(long); 538 strtab = base; 539 base += roundup(strcnt, sizeof(long)); 540 541 if (base > esym || base < ssym) { 542 printf("Symbols are corrupt!\n"); 543 return (EINVAL); 544 } 545 546 ef->ddbsymtab = symtab; 547 ef->ddbsymcnt = symcnt / sizeof(Elf_Sym); 548 ef->ddbstrtab = strtab; 549 ef->ddbstrcnt = strcnt; 550 551 return (0); 552 } 553 554 static int 555 parse_dynamic(elf_file_t ef) 556 { 557 Elf_Dyn *dp; 558 int plttype = DT_REL; 559 560 for (dp = ef->dynamic; dp->d_tag != DT_NULL; dp++) { 561 switch (dp->d_tag) { 562 case DT_HASH: 563 { 564 /* From src/libexec/rtld-elf/rtld.c */ 565 const Elf_Hashelt *hashtab = (const Elf_Hashelt *) 566 (ef->address + dp->d_un.d_ptr); 567 ef->nbuckets = hashtab[0]; 568 ef->nchains = hashtab[1]; 569 ef->buckets = hashtab + 2; 570 ef->chains = ef->buckets + ef->nbuckets; 571 break; 572 } 573 case DT_STRTAB: 574 ef->strtab = (caddr_t) (ef->address + dp->d_un.d_ptr); 575 break; 576 case DT_STRSZ: 577 ef->strsz = dp->d_un.d_val; 578 break; 579 case DT_SYMTAB: 580 ef->symtab = (Elf_Sym*) (ef->address + dp->d_un.d_ptr); 581 break; 582 case DT_SYMENT: 583 if (dp->d_un.d_val != sizeof(Elf_Sym)) 584 return (ENOEXEC); 585 break; 586 case DT_PLTGOT: 587 ef->got = (Elf_Addr *) (ef->address + dp->d_un.d_ptr); 588 break; 589 case DT_REL: 590 ef->rel = (const Elf_Rel *) (ef->address + dp->d_un.d_ptr); 591 break; 592 case DT_RELSZ: 593 ef->relsize = dp->d_un.d_val; 594 break; 595 case DT_RELENT: 596 if (dp->d_un.d_val != sizeof(Elf_Rel)) 597 return (ENOEXEC); 598 break; 599 case DT_JMPREL: 600 ef->pltrel = (const Elf_Rel *) (ef->address + dp->d_un.d_ptr); 601 break; 602 case DT_PLTRELSZ: 603 ef->pltrelsize = dp->d_un.d_val; 604 break; 605 case DT_RELA: 606 ef->rela = (const Elf_Rela *) (ef->address + dp->d_un.d_ptr); 607 break; 608 case DT_RELASZ: 609 ef->relasize = dp->d_un.d_val; 610 break; 611 case DT_RELAENT: 612 if (dp->d_un.d_val != sizeof(Elf_Rela)) 613 return (ENOEXEC); 614 break; 615 case DT_PLTREL: 616 plttype = dp->d_un.d_val; 617 if (plttype != DT_REL && plttype != DT_RELA) 618 return (ENOEXEC); 619 break; 620 #ifdef GDB 621 case DT_DEBUG: 622 dp->d_un.d_ptr = (Elf_Addr)&r_debug; 623 break; 624 #endif 625 } 626 } 627 628 if (plttype == DT_RELA) { 629 ef->pltrela = (const Elf_Rela *)ef->pltrel; 630 ef->pltrel = NULL; 631 ef->pltrelasize = ef->pltrelsize; 632 ef->pltrelsize = 0; 633 } 634 635 ef->ddbsymtab = ef->symtab; 636 ef->ddbsymcnt = ef->nchains; 637 ef->ddbstrtab = ef->strtab; 638 ef->ddbstrcnt = ef->strsz; 639 640 return elf_cpu_parse_dynamic(ef->address, ef->dynamic); 641 } 642 643 #define LS_PADDING 0x90909090 644 static int 645 parse_dpcpu(elf_file_t ef) 646 { 647 int error, size; 648 #if defined(__i386__) 649 uint32_t pad; 650 #endif 651 652 ef->pcpu_start = 0; 653 ef->pcpu_stop = 0; 654 error = link_elf_lookup_set(&ef->lf, "pcpu", (void ***)&ef->pcpu_start, 655 (void ***)&ef->pcpu_stop, NULL); 656 /* Error just means there is no pcpu set to relocate. */ 657 if (error != 0) 658 return (0); 659 size = (uintptr_t)ef->pcpu_stop - (uintptr_t)ef->pcpu_start; 660 /* Empty set? */ 661 if (size < 1) 662 return (0); 663 #if defined(__i386__) 664 /* In case we do find __start/stop_set_ symbols double-check. */ 665 if (size < 4) { 666 uprintf("Kernel module '%s' must be recompiled with " 667 "linker script\n", ef->lf.pathname); 668 return (ENOEXEC); 669 } 670 671 /* Padding from linker-script correct? */ 672 pad = *(uint32_t *)((uintptr_t)ef->pcpu_stop - sizeof(pad)); 673 if (pad != LS_PADDING) { 674 uprintf("Kernel module '%s' must be recompiled with " 675 "linker script, invalid padding %#04x (%#04x)\n", 676 ef->lf.pathname, pad, LS_PADDING); 677 return (ENOEXEC); 678 } 679 /* If we only have valid padding, nothing to do. */ 680 if (size == 4) 681 return (0); 682 #endif 683 /* 684 * Allocate space in the primary pcpu area. Copy in our 685 * initialization from the data section and then initialize 686 * all per-cpu storage from that. 687 */ 688 ef->pcpu_base = (Elf_Addr)(uintptr_t)dpcpu_alloc(size); 689 if (ef->pcpu_base == 0) { 690 printf("%s: pcpu module space is out of space; " 691 "cannot allocate %d for %s\n", 692 __func__, size, ef->lf.pathname); 693 return (ENOSPC); 694 } 695 memcpy((void *)ef->pcpu_base, (void *)ef->pcpu_start, size); 696 dpcpu_copy((void *)ef->pcpu_base, size); 697 elf_set_add(&set_pcpu_list, ef->pcpu_start, ef->pcpu_stop, 698 ef->pcpu_base); 699 700 return (0); 701 } 702 703 #ifdef VIMAGE 704 static int 705 parse_vnet(elf_file_t ef) 706 { 707 int error, size; 708 #if defined(__i386__) 709 uint32_t pad; 710 #endif 711 712 ef->vnet_start = 0; 713 ef->vnet_stop = 0; 714 error = link_elf_lookup_set(&ef->lf, "vnet", (void ***)&ef->vnet_start, 715 (void ***)&ef->vnet_stop, NULL); 716 /* Error just means there is no vnet data set to relocate. */ 717 if (error != 0) 718 return (0); 719 size = (uintptr_t)ef->vnet_stop - (uintptr_t)ef->vnet_start; 720 /* Empty set? */ 721 if (size < 1) 722 return (0); 723 #if defined(__i386__) 724 /* In case we do find __start/stop_set_ symbols double-check. */ 725 if (size < 4) { 726 uprintf("Kernel module '%s' must be recompiled with " 727 "linker script\n", ef->lf.pathname); 728 return (ENOEXEC); 729 } 730 731 /* Padding from linker-script correct? */ 732 pad = *(uint32_t *)((uintptr_t)ef->vnet_stop - sizeof(pad)); 733 if (pad != LS_PADDING) { 734 uprintf("Kernel module '%s' must be recompiled with " 735 "linker script, invalid padding %#04x (%#04x)\n", 736 ef->lf.pathname, pad, LS_PADDING); 737 return (ENOEXEC); 738 } 739 /* If we only have valid padding, nothing to do. */ 740 if (size == 4) 741 return (0); 742 #endif 743 /* 744 * Allocate space in the primary vnet area. Copy in our 745 * initialization from the data section and then initialize 746 * all per-vnet storage from that. 747 */ 748 ef->vnet_base = (Elf_Addr)(uintptr_t)vnet_data_alloc(size); 749 if (ef->vnet_base == 0) { 750 printf("%s: vnet module space is out of space; " 751 "cannot allocate %d for %s\n", 752 __func__, size, ef->lf.pathname); 753 return (ENOSPC); 754 } 755 memcpy((void *)ef->vnet_base, (void *)ef->vnet_start, size); 756 vnet_data_copy((void *)ef->vnet_base, size); 757 elf_set_add(&set_vnet_list, ef->vnet_start, ef->vnet_stop, 758 ef->vnet_base); 759 760 return (0); 761 } 762 #endif 763 #undef LS_PADDING 764 765 /* 766 * Apply the specified protection to the loadable segments of a preloaded linker 767 * file. 768 */ 769 static int 770 preload_protect(elf_file_t ef, vm_prot_t prot) 771 { 772 #if defined(__aarch64__) || defined(__amd64__) 773 Elf_Ehdr *hdr; 774 Elf_Phdr *phdr, *phlimit; 775 vm_prot_t nprot; 776 int error; 777 778 error = 0; 779 hdr = (Elf_Ehdr *)ef->address; 780 phdr = (Elf_Phdr *)(ef->address + hdr->e_phoff); 781 phlimit = phdr + hdr->e_phnum; 782 for (; phdr < phlimit; phdr++) { 783 if (phdr->p_type != PT_LOAD) 784 continue; 785 786 nprot = prot | VM_PROT_READ; 787 if ((phdr->p_flags & PF_W) != 0) 788 nprot |= VM_PROT_WRITE; 789 if ((phdr->p_flags & PF_X) != 0) 790 nprot |= VM_PROT_EXECUTE; 791 error = pmap_change_prot((vm_offset_t)ef->address + 792 phdr->p_vaddr, round_page(phdr->p_memsz), nprot); 793 if (error != 0) 794 break; 795 } 796 return (error); 797 #else 798 return (0); 799 #endif 800 } 801 802 #ifdef __arm__ 803 /* 804 * Locate the ARM exception/unwind table info for DDB and stack(9) use by 805 * searching for the section header that describes it. There may be no unwind 806 * info, for example in a module containing only data. 807 */ 808 static void 809 link_elf_locate_exidx(linker_file_t lf, Elf_Shdr *shdr, int nhdr) 810 { 811 int i; 812 813 for (i = 0; i < nhdr; i++) { 814 if (shdr[i].sh_type == SHT_ARM_EXIDX) { 815 lf->exidx_addr = shdr[i].sh_addr + lf->address; 816 lf->exidx_size = shdr[i].sh_size; 817 break; 818 } 819 } 820 } 821 822 /* 823 * Locate the section headers metadata in a preloaded module, then use it to 824 * locate the exception/unwind table in the module. The size of the metadata 825 * block is stored in a uint32 word immediately before the data itself, and a 826 * comment in preload_search_info() says it is safe to rely on that. 827 */ 828 static void 829 link_elf_locate_exidx_preload(struct linker_file *lf, caddr_t modptr) 830 { 831 uint32_t *modinfo; 832 Elf_Shdr *shdr; 833 uint32_t nhdr; 834 835 modinfo = (uint32_t *)preload_search_info(modptr, 836 MODINFO_METADATA | MODINFOMD_SHDR); 837 if (modinfo != NULL) { 838 shdr = (Elf_Shdr *)modinfo; 839 nhdr = modinfo[-1] / sizeof(Elf_Shdr); 840 link_elf_locate_exidx(lf, shdr, nhdr); 841 } 842 } 843 844 #endif /* __arm__ */ 845 846 static int 847 link_elf_link_preload(linker_class_t cls, const char *filename, 848 linker_file_t *result) 849 { 850 Elf_Addr *ctors_addrp; 851 Elf_Size *ctors_sizep; 852 caddr_t modptr, baseptr, sizeptr, dynptr; 853 char *type; 854 elf_file_t ef; 855 linker_file_t lf; 856 int error; 857 vm_offset_t dp; 858 859 /* Look to see if we have the file preloaded */ 860 modptr = preload_search_by_name(filename); 861 if (modptr == NULL) 862 return (ENOENT); 863 864 type = (char *)preload_search_info(modptr, MODINFO_TYPE); 865 baseptr = preload_search_info(modptr, MODINFO_ADDR); 866 sizeptr = preload_search_info(modptr, MODINFO_SIZE); 867 dynptr = preload_search_info(modptr, 868 MODINFO_METADATA | MODINFOMD_DYNAMIC); 869 if (type == NULL || 870 (strcmp(type, "elf" __XSTRING(__ELF_WORD_SIZE) " module") != 0 && 871 strcmp(type, "elf module") != 0)) 872 return (EFTYPE); 873 if (baseptr == NULL || sizeptr == NULL || dynptr == NULL) 874 return (EINVAL); 875 876 lf = linker_make_file(filename, &link_elf_class); 877 if (lf == NULL) 878 return (ENOMEM); 879 880 ef = (elf_file_t) lf; 881 ef->preloaded = 1; 882 ef->modptr = modptr; 883 ef->address = *(caddr_t *)baseptr; 884 #ifdef SPARSE_MAPPING 885 ef->object = NULL; 886 #endif 887 dp = (vm_offset_t)ef->address + *(vm_offset_t *)dynptr; 888 ef->dynamic = (Elf_Dyn *)dp; 889 lf->address = ef->address; 890 lf->size = *(size_t *)sizeptr; 891 892 ctors_addrp = (Elf_Addr *)preload_search_info(modptr, 893 MODINFO_METADATA | MODINFOMD_CTORS_ADDR); 894 ctors_sizep = (Elf_Size *)preload_search_info(modptr, 895 MODINFO_METADATA | MODINFOMD_CTORS_SIZE); 896 if (ctors_addrp != NULL && ctors_sizep != NULL) { 897 lf->ctors_addr = ef->address + *ctors_addrp; 898 lf->ctors_size = *ctors_sizep; 899 } 900 901 #ifdef __arm__ 902 link_elf_locate_exidx_preload(lf, modptr); 903 #endif 904 905 error = parse_dynamic(ef); 906 if (error == 0) 907 error = parse_dpcpu(ef); 908 #ifdef VIMAGE 909 if (error == 0) 910 error = parse_vnet(ef); 911 #endif 912 if (error == 0) 913 error = preload_protect(ef, VM_PROT_ALL); 914 if (error != 0) { 915 linker_file_unload(lf, LINKER_UNLOAD_FORCE); 916 return (error); 917 } 918 link_elf_reloc_local(lf); 919 *result = lf; 920 return (0); 921 } 922 923 static int 924 link_elf_link_preload_finish(linker_file_t lf) 925 { 926 elf_file_t ef; 927 int error; 928 929 ef = (elf_file_t) lf; 930 error = relocate_file(ef); 931 if (error == 0) 932 error = preload_protect(ef, VM_PROT_NONE); 933 if (error != 0) 934 return (error); 935 (void)link_elf_preload_parse_symbols(ef); 936 937 return (link_elf_link_common_finish(lf)); 938 } 939 940 static int 941 link_elf_load_file(linker_class_t cls, const char* filename, 942 linker_file_t* result) 943 { 944 struct nameidata nd; 945 struct thread* td = curthread; /* XXX */ 946 Elf_Ehdr *hdr; 947 caddr_t firstpage, segbase; 948 int nbytes, i; 949 Elf_Phdr *phdr; 950 Elf_Phdr *phlimit; 951 Elf_Phdr *segs[MAXSEGS]; 952 int nsegs; 953 Elf_Phdr *phdyn; 954 caddr_t mapbase; 955 size_t mapsize; 956 Elf_Addr base_vaddr; 957 Elf_Addr base_vlimit; 958 int error = 0; 959 ssize_t resid; 960 int flags; 961 elf_file_t ef; 962 linker_file_t lf; 963 Elf_Shdr *shdr; 964 int symtabindex; 965 int symstrindex; 966 int shstrindex; 967 int symcnt; 968 int strcnt; 969 char *shstrs; 970 971 shdr = NULL; 972 lf = NULL; 973 shstrs = NULL; 974 975 NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, filename, td); 976 flags = FREAD; 977 error = vn_open(&nd, &flags, 0, NULL); 978 if (error != 0) 979 return (error); 980 NDFREE(&nd, NDF_ONLY_PNBUF); 981 if (nd.ni_vp->v_type != VREG) { 982 error = ENOEXEC; 983 firstpage = NULL; 984 goto out; 985 } 986 #ifdef MAC 987 error = mac_kld_check_load(curthread->td_ucred, nd.ni_vp); 988 if (error != 0) { 989 firstpage = NULL; 990 goto out; 991 } 992 #endif 993 994 /* 995 * Read the elf header from the file. 996 */ 997 firstpage = malloc(PAGE_SIZE, M_LINKER, M_WAITOK); 998 hdr = (Elf_Ehdr *)firstpage; 999 error = vn_rdwr(UIO_READ, nd.ni_vp, firstpage, PAGE_SIZE, 0, 1000 UIO_SYSSPACE, IO_NODELOCKED, td->td_ucred, NOCRED, 1001 &resid, td); 1002 nbytes = PAGE_SIZE - resid; 1003 if (error != 0) 1004 goto out; 1005 1006 if (!IS_ELF(*hdr)) { 1007 error = ENOEXEC; 1008 goto out; 1009 } 1010 1011 if (hdr->e_ident[EI_CLASS] != ELF_TARG_CLASS || 1012 hdr->e_ident[EI_DATA] != ELF_TARG_DATA) { 1013 link_elf_error(filename, "Unsupported file layout"); 1014 error = ENOEXEC; 1015 goto out; 1016 } 1017 if (hdr->e_ident[EI_VERSION] != EV_CURRENT || 1018 hdr->e_version != EV_CURRENT) { 1019 link_elf_error(filename, "Unsupported file version"); 1020 error = ENOEXEC; 1021 goto out; 1022 } 1023 if (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN) { 1024 error = ENOSYS; 1025 goto out; 1026 } 1027 if (hdr->e_machine != ELF_TARG_MACH) { 1028 link_elf_error(filename, "Unsupported machine"); 1029 error = ENOEXEC; 1030 goto out; 1031 } 1032 1033 /* 1034 * We rely on the program header being in the first page. 1035 * This is not strictly required by the ABI specification, but 1036 * it seems to always true in practice. And, it simplifies 1037 * things considerably. 1038 */ 1039 if (!((hdr->e_phentsize == sizeof(Elf_Phdr)) && 1040 (hdr->e_phoff + hdr->e_phnum*sizeof(Elf_Phdr) <= PAGE_SIZE) && 1041 (hdr->e_phoff + hdr->e_phnum*sizeof(Elf_Phdr) <= nbytes))) 1042 link_elf_error(filename, "Unreadable program headers"); 1043 1044 /* 1045 * Scan the program header entries, and save key information. 1046 * 1047 * We rely on there being exactly two load segments, text and data, 1048 * in that order. 1049 */ 1050 phdr = (Elf_Phdr *) (firstpage + hdr->e_phoff); 1051 phlimit = phdr + hdr->e_phnum; 1052 nsegs = 0; 1053 phdyn = NULL; 1054 while (phdr < phlimit) { 1055 switch (phdr->p_type) { 1056 case PT_LOAD: 1057 if (nsegs == MAXSEGS) { 1058 link_elf_error(filename, "Too many sections"); 1059 error = ENOEXEC; 1060 goto out; 1061 } 1062 /* 1063 * XXX: We just trust they come in right order ?? 1064 */ 1065 segs[nsegs] = phdr; 1066 ++nsegs; 1067 break; 1068 1069 case PT_DYNAMIC: 1070 phdyn = phdr; 1071 break; 1072 1073 case PT_INTERP: 1074 error = ENOSYS; 1075 goto out; 1076 } 1077 1078 ++phdr; 1079 } 1080 if (phdyn == NULL) { 1081 link_elf_error(filename, "Object is not dynamically-linked"); 1082 error = ENOEXEC; 1083 goto out; 1084 } 1085 if (nsegs == 0) { 1086 link_elf_error(filename, "No sections"); 1087 error = ENOEXEC; 1088 goto out; 1089 } 1090 1091 /* 1092 * Allocate the entire address space of the object, to stake 1093 * out our contiguous region, and to establish the base 1094 * address for relocation. 1095 */ 1096 base_vaddr = trunc_page(segs[0]->p_vaddr); 1097 base_vlimit = round_page(segs[nsegs - 1]->p_vaddr + 1098 segs[nsegs - 1]->p_memsz); 1099 mapsize = base_vlimit - base_vaddr; 1100 1101 lf = linker_make_file(filename, &link_elf_class); 1102 if (lf == NULL) { 1103 error = ENOMEM; 1104 goto out; 1105 } 1106 1107 ef = (elf_file_t) lf; 1108 #ifdef SPARSE_MAPPING 1109 ef->object = vm_pager_allocate(OBJT_PHYS, NULL, mapsize, VM_PROT_ALL, 1110 0, thread0.td_ucred); 1111 if (ef->object == NULL) { 1112 error = ENOMEM; 1113 goto out; 1114 } 1115 #ifdef __amd64__ 1116 mapbase = (caddr_t)KERNBASE; 1117 #else 1118 mapbase = (caddr_t)vm_map_min(kernel_map); 1119 #endif 1120 /* 1121 * Mapping protections are downgraded after relocation processing. 1122 */ 1123 error = vm_map_find(kernel_map, ef->object, 0, 1124 (vm_offset_t *)&mapbase, mapsize, 0, VMFS_OPTIMAL_SPACE, 1125 VM_PROT_ALL, VM_PROT_ALL, 0); 1126 if (error != 0) { 1127 vm_object_deallocate(ef->object); 1128 ef->object = NULL; 1129 goto out; 1130 } 1131 #else 1132 mapbase = malloc_exec(mapsize, M_LINKER, M_WAITOK); 1133 #endif 1134 ef->address = mapbase; 1135 1136 /* 1137 * Read the text and data sections and zero the bss. 1138 */ 1139 for (i = 0; i < nsegs; i++) { 1140 segbase = mapbase + segs[i]->p_vaddr - base_vaddr; 1141 1142 #ifdef SPARSE_MAPPING 1143 /* 1144 * Consecutive segments may have different mapping permissions, 1145 * so be strict and verify that their mappings do not overlap. 1146 */ 1147 if (((vm_offset_t)segbase & PAGE_MASK) != 0) { 1148 error = EINVAL; 1149 goto out; 1150 } 1151 1152 error = vm_map_wire(kernel_map, 1153 (vm_offset_t)segbase, 1154 (vm_offset_t)segbase + round_page(segs[i]->p_memsz), 1155 VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES); 1156 if (error != KERN_SUCCESS) { 1157 error = ENOMEM; 1158 goto out; 1159 } 1160 #endif 1161 1162 error = vn_rdwr(UIO_READ, nd.ni_vp, 1163 segbase, segs[i]->p_filesz, segs[i]->p_offset, 1164 UIO_SYSSPACE, IO_NODELOCKED, td->td_ucred, NOCRED, 1165 &resid, td); 1166 if (error != 0) 1167 goto out; 1168 bzero(segbase + segs[i]->p_filesz, 1169 segs[i]->p_memsz - segs[i]->p_filesz); 1170 } 1171 1172 #ifdef GPROF 1173 /* Update profiling information with the new text segment. */ 1174 mtx_lock(&Giant); 1175 kmupetext((uintfptr_t)(mapbase + segs[0]->p_vaddr - base_vaddr + 1176 segs[0]->p_memsz)); 1177 mtx_unlock(&Giant); 1178 #endif 1179 1180 ef->dynamic = (Elf_Dyn *) (mapbase + phdyn->p_vaddr - base_vaddr); 1181 1182 lf->address = ef->address; 1183 lf->size = mapsize; 1184 1185 error = parse_dynamic(ef); 1186 if (error != 0) 1187 goto out; 1188 error = parse_dpcpu(ef); 1189 if (error != 0) 1190 goto out; 1191 #ifdef VIMAGE 1192 error = parse_vnet(ef); 1193 if (error != 0) 1194 goto out; 1195 #endif 1196 link_elf_reloc_local(lf); 1197 1198 VOP_UNLOCK(nd.ni_vp); 1199 error = linker_load_dependencies(lf); 1200 vn_lock(nd.ni_vp, LK_EXCLUSIVE | LK_RETRY); 1201 if (error != 0) 1202 goto out; 1203 error = relocate_file(ef); 1204 if (error != 0) 1205 goto out; 1206 1207 #ifdef SPARSE_MAPPING 1208 /* 1209 * Downgrade permissions on text segment mappings now that relocation 1210 * processing is complete. Restrict permissions on read-only segments. 1211 */ 1212 for (i = 0; i < nsegs; i++) { 1213 vm_prot_t prot; 1214 1215 if (segs[i]->p_type != PT_LOAD) 1216 continue; 1217 1218 prot = VM_PROT_READ; 1219 if ((segs[i]->p_flags & PF_W) != 0) 1220 prot |= VM_PROT_WRITE; 1221 if ((segs[i]->p_flags & PF_X) != 0) 1222 prot |= VM_PROT_EXECUTE; 1223 segbase = mapbase + segs[i]->p_vaddr - base_vaddr; 1224 error = vm_map_protect(kernel_map, 1225 (vm_offset_t)segbase, 1226 (vm_offset_t)segbase + round_page(segs[i]->p_memsz), 1227 prot, 0, VM_MAP_PROTECT_SET_PROT); 1228 if (error != KERN_SUCCESS) { 1229 error = ENOMEM; 1230 goto out; 1231 } 1232 } 1233 #endif 1234 1235 /* 1236 * Try and load the symbol table if it's present. (you can 1237 * strip it!) 1238 */ 1239 nbytes = hdr->e_shnum * hdr->e_shentsize; 1240 if (nbytes == 0 || hdr->e_shoff == 0) 1241 goto nosyms; 1242 shdr = malloc(nbytes, M_LINKER, M_WAITOK | M_ZERO); 1243 error = vn_rdwr(UIO_READ, nd.ni_vp, 1244 (caddr_t)shdr, nbytes, hdr->e_shoff, 1245 UIO_SYSSPACE, IO_NODELOCKED, td->td_ucred, NOCRED, 1246 &resid, td); 1247 if (error != 0) 1248 goto out; 1249 1250 /* Read section string table */ 1251 shstrindex = hdr->e_shstrndx; 1252 if (shstrindex != 0 && shdr[shstrindex].sh_type == SHT_STRTAB && 1253 shdr[shstrindex].sh_size != 0) { 1254 nbytes = shdr[shstrindex].sh_size; 1255 shstrs = malloc(nbytes, M_LINKER, M_WAITOK | M_ZERO); 1256 error = vn_rdwr(UIO_READ, nd.ni_vp, (caddr_t)shstrs, nbytes, 1257 shdr[shstrindex].sh_offset, UIO_SYSSPACE, IO_NODELOCKED, 1258 td->td_ucred, NOCRED, &resid, td); 1259 if (error) 1260 goto out; 1261 } 1262 1263 symtabindex = -1; 1264 symstrindex = -1; 1265 for (i = 0; i < hdr->e_shnum; i++) { 1266 if (shdr[i].sh_type == SHT_SYMTAB) { 1267 symtabindex = i; 1268 symstrindex = shdr[i].sh_link; 1269 } else if (shstrs != NULL && shdr[i].sh_name != 0 && 1270 strcmp(shstrs + shdr[i].sh_name, ".ctors") == 0) { 1271 /* Record relocated address and size of .ctors. */ 1272 lf->ctors_addr = mapbase + shdr[i].sh_addr - base_vaddr; 1273 lf->ctors_size = shdr[i].sh_size; 1274 } 1275 } 1276 if (symtabindex < 0 || symstrindex < 0) 1277 goto nosyms; 1278 1279 symcnt = shdr[symtabindex].sh_size; 1280 ef->symbase = malloc(symcnt, M_LINKER, M_WAITOK); 1281 strcnt = shdr[symstrindex].sh_size; 1282 ef->strbase = malloc(strcnt, M_LINKER, M_WAITOK); 1283 1284 error = vn_rdwr(UIO_READ, nd.ni_vp, 1285 ef->symbase, symcnt, shdr[symtabindex].sh_offset, 1286 UIO_SYSSPACE, IO_NODELOCKED, td->td_ucred, NOCRED, 1287 &resid, td); 1288 if (error != 0) 1289 goto out; 1290 error = vn_rdwr(UIO_READ, nd.ni_vp, 1291 ef->strbase, strcnt, shdr[symstrindex].sh_offset, 1292 UIO_SYSSPACE, IO_NODELOCKED, td->td_ucred, NOCRED, 1293 &resid, td); 1294 if (error != 0) 1295 goto out; 1296 1297 ef->ddbsymcnt = symcnt / sizeof(Elf_Sym); 1298 ef->ddbsymtab = (const Elf_Sym *)ef->symbase; 1299 ef->ddbstrcnt = strcnt; 1300 ef->ddbstrtab = ef->strbase; 1301 1302 nosyms: 1303 1304 #ifdef __arm__ 1305 link_elf_locate_exidx(lf, shdr, hdr->e_shnum); 1306 #endif 1307 1308 error = link_elf_link_common_finish(lf); 1309 if (error != 0) 1310 goto out; 1311 1312 *result = lf; 1313 1314 out: 1315 VOP_UNLOCK(nd.ni_vp); 1316 vn_close(nd.ni_vp, FREAD, td->td_ucred, td); 1317 if (error != 0 && lf != NULL) 1318 linker_file_unload(lf, LINKER_UNLOAD_FORCE); 1319 free(shdr, M_LINKER); 1320 free(firstpage, M_LINKER); 1321 free(shstrs, M_LINKER); 1322 1323 return (error); 1324 } 1325 1326 Elf_Addr 1327 elf_relocaddr(linker_file_t lf, Elf_Addr x) 1328 { 1329 elf_file_t ef; 1330 1331 KASSERT(lf->ops->cls == (kobj_class_t)&link_elf_class, 1332 ("elf_relocaddr: unexpected linker file %p", lf)); 1333 1334 ef = (elf_file_t)lf; 1335 if (x >= ef->pcpu_start && x < ef->pcpu_stop) 1336 return ((x - ef->pcpu_start) + ef->pcpu_base); 1337 #ifdef VIMAGE 1338 if (x >= ef->vnet_start && x < ef->vnet_stop) 1339 return ((x - ef->vnet_start) + ef->vnet_base); 1340 #endif 1341 return (x); 1342 } 1343 1344 static void 1345 link_elf_unload_file(linker_file_t file) 1346 { 1347 elf_file_t ef = (elf_file_t) file; 1348 1349 if (ef->pcpu_base != 0) { 1350 dpcpu_free((void *)ef->pcpu_base, 1351 ef->pcpu_stop - ef->pcpu_start); 1352 elf_set_delete(&set_pcpu_list, ef->pcpu_start); 1353 } 1354 #ifdef VIMAGE 1355 if (ef->vnet_base != 0) { 1356 vnet_data_free((void *)ef->vnet_base, 1357 ef->vnet_stop - ef->vnet_start); 1358 elf_set_delete(&set_vnet_list, ef->vnet_start); 1359 } 1360 #endif 1361 #ifdef GDB 1362 if (ef->gdb.l_ld != NULL) { 1363 GDB_STATE(RT_DELETE); 1364 free((void *)(uintptr_t)ef->gdb.l_name, M_LINKER); 1365 link_elf_delete_gdb(&ef->gdb); 1366 GDB_STATE(RT_CONSISTENT); 1367 } 1368 #endif 1369 1370 /* Notify MD code that a module is being unloaded. */ 1371 elf_cpu_unload_file(file); 1372 1373 if (ef->preloaded) { 1374 link_elf_unload_preload(file); 1375 return; 1376 } 1377 1378 #ifdef SPARSE_MAPPING 1379 if (ef->object != NULL) { 1380 vm_map_remove(kernel_map, (vm_offset_t) ef->address, 1381 (vm_offset_t) ef->address 1382 + (ef->object->size << PAGE_SHIFT)); 1383 } 1384 #else 1385 free(ef->address, M_LINKER); 1386 #endif 1387 free(ef->symbase, M_LINKER); 1388 free(ef->strbase, M_LINKER); 1389 free(ef->ctftab, M_LINKER); 1390 free(ef->ctfoff, M_LINKER); 1391 free(ef->typoff, M_LINKER); 1392 } 1393 1394 static void 1395 link_elf_unload_preload(linker_file_t file) 1396 { 1397 1398 if (file->pathname != NULL) 1399 preload_delete_name(file->pathname); 1400 } 1401 1402 static const char * 1403 symbol_name(elf_file_t ef, Elf_Size r_info) 1404 { 1405 const Elf_Sym *ref; 1406 1407 if (ELF_R_SYM(r_info)) { 1408 ref = ef->symtab + ELF_R_SYM(r_info); 1409 return (ef->strtab + ref->st_name); 1410 } 1411 return (NULL); 1412 } 1413 1414 static int 1415 symbol_type(elf_file_t ef, Elf_Size r_info) 1416 { 1417 const Elf_Sym *ref; 1418 1419 if (ELF_R_SYM(r_info)) { 1420 ref = ef->symtab + ELF_R_SYM(r_info); 1421 return (ELF_ST_TYPE(ref->st_info)); 1422 } 1423 return (STT_NOTYPE); 1424 } 1425 1426 static int 1427 relocate_file1(elf_file_t ef, elf_lookup_fn lookup, elf_reloc_fn reloc, 1428 bool ifuncs) 1429 { 1430 const Elf_Rel *rel; 1431 const Elf_Rela *rela; 1432 const char *symname; 1433 1434 #define APPLY_RELOCS(iter, tbl, tblsize, type) do { \ 1435 for ((iter) = (tbl); (iter) != NULL && \ 1436 (iter) < (tbl) + (tblsize) / sizeof(*(iter)); (iter)++) { \ 1437 if ((symbol_type(ef, (iter)->r_info) == \ 1438 STT_GNU_IFUNC || \ 1439 elf_is_ifunc_reloc((iter)->r_info)) != ifuncs) \ 1440 continue; \ 1441 if (reloc(&ef->lf, (Elf_Addr)ef->address, \ 1442 (iter), (type), lookup)) { \ 1443 symname = symbol_name(ef, (iter)->r_info); \ 1444 printf("link_elf: symbol %s undefined\n", \ 1445 symname); \ 1446 return (ENOENT); \ 1447 } \ 1448 } \ 1449 } while (0) 1450 1451 APPLY_RELOCS(rel, ef->rel, ef->relsize, ELF_RELOC_REL); 1452 APPLY_RELOCS(rela, ef->rela, ef->relasize, ELF_RELOC_RELA); 1453 APPLY_RELOCS(rel, ef->pltrel, ef->pltrelsize, ELF_RELOC_REL); 1454 APPLY_RELOCS(rela, ef->pltrela, ef->pltrelasize, ELF_RELOC_RELA); 1455 1456 #undef APPLY_RELOCS 1457 1458 return (0); 1459 } 1460 1461 static int 1462 relocate_file(elf_file_t ef) 1463 { 1464 int error; 1465 1466 error = relocate_file1(ef, elf_lookup, elf_reloc, false); 1467 if (error == 0) 1468 error = relocate_file1(ef, elf_lookup, elf_reloc, true); 1469 return (error); 1470 } 1471 1472 /* 1473 * Hash function for symbol table lookup. Don't even think about changing 1474 * this. It is specified by the System V ABI. 1475 */ 1476 static unsigned long 1477 elf_hash(const char *name) 1478 { 1479 const unsigned char *p = (const unsigned char *) name; 1480 unsigned long h = 0; 1481 unsigned long g; 1482 1483 while (*p != '\0') { 1484 h = (h << 4) + *p++; 1485 if ((g = h & 0xf0000000) != 0) 1486 h ^= g >> 24; 1487 h &= ~g; 1488 } 1489 return (h); 1490 } 1491 1492 static int 1493 link_elf_lookup_symbol(linker_file_t lf, const char *name, c_linker_sym_t *sym) 1494 { 1495 elf_file_t ef = (elf_file_t) lf; 1496 unsigned long symnum; 1497 const Elf_Sym* symp; 1498 const char *strp; 1499 unsigned long hash; 1500 int i; 1501 1502 /* If we don't have a hash, bail. */ 1503 if (ef->buckets == NULL || ef->nbuckets == 0) { 1504 printf("link_elf_lookup_symbol: missing symbol hash table\n"); 1505 return (ENOENT); 1506 } 1507 1508 /* First, search hashed global symbols */ 1509 hash = elf_hash(name); 1510 symnum = ef->buckets[hash % ef->nbuckets]; 1511 1512 while (symnum != STN_UNDEF) { 1513 if (symnum >= ef->nchains) { 1514 printf("%s: corrupt symbol table\n", __func__); 1515 return (ENOENT); 1516 } 1517 1518 symp = ef->symtab + symnum; 1519 if (symp->st_name == 0) { 1520 printf("%s: corrupt symbol table\n", __func__); 1521 return (ENOENT); 1522 } 1523 1524 strp = ef->strtab + symp->st_name; 1525 1526 if (strcmp(name, strp) == 0) { 1527 if (symp->st_shndx != SHN_UNDEF || 1528 (symp->st_value != 0 && 1529 (ELF_ST_TYPE(symp->st_info) == STT_FUNC || 1530 ELF_ST_TYPE(symp->st_info) == STT_GNU_IFUNC))) { 1531 *sym = (c_linker_sym_t) symp; 1532 return (0); 1533 } 1534 return (ENOENT); 1535 } 1536 1537 symnum = ef->chains[symnum]; 1538 } 1539 1540 /* If we have not found it, look at the full table (if loaded) */ 1541 if (ef->symtab == ef->ddbsymtab) 1542 return (ENOENT); 1543 1544 /* Exhaustive search */ 1545 for (i = 0, symp = ef->ddbsymtab; i < ef->ddbsymcnt; i++, symp++) { 1546 strp = ef->ddbstrtab + symp->st_name; 1547 if (strcmp(name, strp) == 0) { 1548 if (symp->st_shndx != SHN_UNDEF || 1549 (symp->st_value != 0 && 1550 (ELF_ST_TYPE(symp->st_info) == STT_FUNC || 1551 ELF_ST_TYPE(symp->st_info) == STT_GNU_IFUNC))) { 1552 *sym = (c_linker_sym_t) symp; 1553 return (0); 1554 } 1555 return (ENOENT); 1556 } 1557 } 1558 1559 return (ENOENT); 1560 } 1561 1562 static int 1563 link_elf_symbol_values(linker_file_t lf, c_linker_sym_t sym, 1564 linker_symval_t *symval) 1565 { 1566 elf_file_t ef; 1567 const Elf_Sym *es; 1568 caddr_t val; 1569 1570 ef = (elf_file_t)lf; 1571 es = (const Elf_Sym *)sym; 1572 if (es >= ef->symtab && es < (ef->symtab + ef->nchains)) { 1573 symval->name = ef->strtab + es->st_name; 1574 val = (caddr_t)ef->address + es->st_value; 1575 if (ELF_ST_TYPE(es->st_info) == STT_GNU_IFUNC) 1576 val = ((caddr_t (*)(void))val)(); 1577 symval->value = val; 1578 symval->size = es->st_size; 1579 return (0); 1580 } 1581 if (ef->symtab == ef->ddbsymtab) 1582 return (ENOENT); 1583 if (es >= ef->ddbsymtab && es < (ef->ddbsymtab + ef->ddbsymcnt)) { 1584 symval->name = ef->ddbstrtab + es->st_name; 1585 val = (caddr_t)ef->address + es->st_value; 1586 if (ELF_ST_TYPE(es->st_info) == STT_GNU_IFUNC) 1587 val = ((caddr_t (*)(void))val)(); 1588 symval->value = val; 1589 symval->size = es->st_size; 1590 return (0); 1591 } 1592 return (ENOENT); 1593 } 1594 1595 static int 1596 link_elf_search_symbol(linker_file_t lf, caddr_t value, 1597 c_linker_sym_t *sym, long *diffp) 1598 { 1599 elf_file_t ef = (elf_file_t)lf; 1600 u_long off = (uintptr_t) (void *)value; 1601 u_long diff = off; 1602 u_long st_value; 1603 const Elf_Sym *es; 1604 const Elf_Sym *best = NULL; 1605 int i; 1606 1607 for (i = 0, es = ef->ddbsymtab; i < ef->ddbsymcnt; i++, es++) { 1608 if (es->st_name == 0) 1609 continue; 1610 st_value = es->st_value + (uintptr_t) (void *) ef->address; 1611 if (off >= st_value) { 1612 if (off - st_value < diff) { 1613 diff = off - st_value; 1614 best = es; 1615 if (diff == 0) 1616 break; 1617 } else if (off - st_value == diff) { 1618 best = es; 1619 } 1620 } 1621 } 1622 if (best == NULL) 1623 *diffp = off; 1624 else 1625 *diffp = diff; 1626 *sym = (c_linker_sym_t) best; 1627 1628 return (0); 1629 } 1630 1631 /* 1632 * Look up a linker set on an ELF system. 1633 */ 1634 static int 1635 link_elf_lookup_set(linker_file_t lf, const char *name, 1636 void ***startp, void ***stopp, int *countp) 1637 { 1638 c_linker_sym_t sym; 1639 linker_symval_t symval; 1640 char *setsym; 1641 void **start, **stop; 1642 int len, error = 0, count; 1643 1644 len = strlen(name) + sizeof("__start_set_"); /* sizeof includes \0 */ 1645 setsym = malloc(len, M_LINKER, M_WAITOK); 1646 1647 /* get address of first entry */ 1648 snprintf(setsym, len, "%s%s", "__start_set_", name); 1649 error = link_elf_lookup_symbol(lf, setsym, &sym); 1650 if (error != 0) 1651 goto out; 1652 link_elf_symbol_values(lf, sym, &symval); 1653 if (symval.value == 0) { 1654 error = ESRCH; 1655 goto out; 1656 } 1657 start = (void **)symval.value; 1658 1659 /* get address of last entry */ 1660 snprintf(setsym, len, "%s%s", "__stop_set_", name); 1661 error = link_elf_lookup_symbol(lf, setsym, &sym); 1662 if (error != 0) 1663 goto out; 1664 link_elf_symbol_values(lf, sym, &symval); 1665 if (symval.value == 0) { 1666 error = ESRCH; 1667 goto out; 1668 } 1669 stop = (void **)symval.value; 1670 1671 /* and the number of entries */ 1672 count = stop - start; 1673 1674 /* and copy out */ 1675 if (startp != NULL) 1676 *startp = start; 1677 if (stopp != NULL) 1678 *stopp = stop; 1679 if (countp != NULL) 1680 *countp = count; 1681 1682 out: 1683 free(setsym, M_LINKER); 1684 return (error); 1685 } 1686 1687 static int 1688 link_elf_each_function_name(linker_file_t file, 1689 int (*callback)(const char *, void *), void *opaque) 1690 { 1691 elf_file_t ef = (elf_file_t)file; 1692 const Elf_Sym *symp; 1693 int i, error; 1694 1695 /* Exhaustive search */ 1696 for (i = 0, symp = ef->ddbsymtab; i < ef->ddbsymcnt; i++, symp++) { 1697 if (symp->st_value != 0 && 1698 (ELF_ST_TYPE(symp->st_info) == STT_FUNC || 1699 ELF_ST_TYPE(symp->st_info) == STT_GNU_IFUNC)) { 1700 error = callback(ef->ddbstrtab + symp->st_name, opaque); 1701 if (error != 0) 1702 return (error); 1703 } 1704 } 1705 return (0); 1706 } 1707 1708 static int 1709 link_elf_each_function_nameval(linker_file_t file, 1710 linker_function_nameval_callback_t callback, void *opaque) 1711 { 1712 linker_symval_t symval; 1713 elf_file_t ef = (elf_file_t)file; 1714 const Elf_Sym *symp; 1715 int i, error; 1716 1717 /* Exhaustive search */ 1718 for (i = 0, symp = ef->ddbsymtab; i < ef->ddbsymcnt; i++, symp++) { 1719 if (symp->st_value != 0 && 1720 (ELF_ST_TYPE(symp->st_info) == STT_FUNC || 1721 ELF_ST_TYPE(symp->st_info) == STT_GNU_IFUNC)) { 1722 error = link_elf_symbol_values(file, 1723 (c_linker_sym_t) symp, &symval); 1724 if (error != 0) 1725 return (error); 1726 error = callback(file, i, &symval, opaque); 1727 if (error != 0) 1728 return (error); 1729 } 1730 } 1731 return (0); 1732 } 1733 1734 const Elf_Sym * 1735 elf_get_sym(linker_file_t lf, Elf_Size symidx) 1736 { 1737 elf_file_t ef = (elf_file_t)lf; 1738 1739 if (symidx >= ef->nchains) 1740 return (NULL); 1741 return (ef->symtab + symidx); 1742 } 1743 1744 const char * 1745 elf_get_symname(linker_file_t lf, Elf_Size symidx) 1746 { 1747 elf_file_t ef = (elf_file_t)lf; 1748 const Elf_Sym *sym; 1749 1750 if (symidx >= ef->nchains) 1751 return (NULL); 1752 sym = ef->symtab + symidx; 1753 return (ef->strtab + sym->st_name); 1754 } 1755 1756 /* 1757 * Symbol lookup function that can be used when the symbol index is known (ie 1758 * in relocations). It uses the symbol index instead of doing a fully fledged 1759 * hash table based lookup when such is valid. For example for local symbols. 1760 * This is not only more efficient, it's also more correct. It's not always 1761 * the case that the symbol can be found through the hash table. 1762 */ 1763 static int 1764 elf_lookup(linker_file_t lf, Elf_Size symidx, int deps, Elf_Addr *res) 1765 { 1766 elf_file_t ef = (elf_file_t)lf; 1767 const Elf_Sym *sym; 1768 const char *symbol; 1769 Elf_Addr addr, start, base; 1770 1771 /* Don't even try to lookup the symbol if the index is bogus. */ 1772 if (symidx >= ef->nchains) { 1773 *res = 0; 1774 return (EINVAL); 1775 } 1776 1777 sym = ef->symtab + symidx; 1778 1779 /* 1780 * Don't do a full lookup when the symbol is local. It may even 1781 * fail because it may not be found through the hash table. 1782 */ 1783 if (ELF_ST_BIND(sym->st_info) == STB_LOCAL) { 1784 /* Force lookup failure when we have an insanity. */ 1785 if (sym->st_shndx == SHN_UNDEF || sym->st_value == 0) { 1786 *res = 0; 1787 return (EINVAL); 1788 } 1789 *res = ((Elf_Addr)ef->address + sym->st_value); 1790 return (0); 1791 } 1792 1793 /* 1794 * XXX we can avoid doing a hash table based lookup for global 1795 * symbols as well. This however is not always valid, so we'll 1796 * just do it the hard way for now. Performance tweaks can 1797 * always be added. 1798 */ 1799 1800 symbol = ef->strtab + sym->st_name; 1801 1802 /* Force a lookup failure if the symbol name is bogus. */ 1803 if (*symbol == 0) { 1804 *res = 0; 1805 return (EINVAL); 1806 } 1807 1808 addr = ((Elf_Addr)linker_file_lookup_symbol(lf, symbol, deps)); 1809 if (addr == 0 && ELF_ST_BIND(sym->st_info) != STB_WEAK) { 1810 *res = 0; 1811 return (EINVAL); 1812 } 1813 1814 if (elf_set_find(&set_pcpu_list, addr, &start, &base)) 1815 addr = addr - start + base; 1816 #ifdef VIMAGE 1817 else if (elf_set_find(&set_vnet_list, addr, &start, &base)) 1818 addr = addr - start + base; 1819 #endif 1820 *res = addr; 1821 return (0); 1822 } 1823 1824 static void 1825 link_elf_reloc_local(linker_file_t lf) 1826 { 1827 const Elf_Rel *rellim; 1828 const Elf_Rel *rel; 1829 const Elf_Rela *relalim; 1830 const Elf_Rela *rela; 1831 elf_file_t ef = (elf_file_t)lf; 1832 1833 /* Perform relocations without addend if there are any: */ 1834 if ((rel = ef->rel) != NULL) { 1835 rellim = (const Elf_Rel *)((const char *)ef->rel + ef->relsize); 1836 while (rel < rellim) { 1837 elf_reloc_local(lf, (Elf_Addr)ef->address, rel, 1838 ELF_RELOC_REL, elf_lookup); 1839 rel++; 1840 } 1841 } 1842 1843 /* Perform relocations with addend if there are any: */ 1844 if ((rela = ef->rela) != NULL) { 1845 relalim = (const Elf_Rela *) 1846 ((const char *)ef->rela + ef->relasize); 1847 while (rela < relalim) { 1848 elf_reloc_local(lf, (Elf_Addr)ef->address, rela, 1849 ELF_RELOC_RELA, elf_lookup); 1850 rela++; 1851 } 1852 } 1853 } 1854 1855 static long 1856 link_elf_symtab_get(linker_file_t lf, const Elf_Sym **symtab) 1857 { 1858 elf_file_t ef = (elf_file_t)lf; 1859 1860 *symtab = ef->ddbsymtab; 1861 1862 if (*symtab == NULL) 1863 return (0); 1864 1865 return (ef->ddbsymcnt); 1866 } 1867 1868 static long 1869 link_elf_strtab_get(linker_file_t lf, caddr_t *strtab) 1870 { 1871 elf_file_t ef = (elf_file_t)lf; 1872 1873 *strtab = ef->ddbstrtab; 1874 1875 if (*strtab == NULL) 1876 return (0); 1877 1878 return (ef->ddbstrcnt); 1879 } 1880 1881 #if defined(__i386__) || defined(__amd64__) || defined(__aarch64__) || defined(__powerpc__) 1882 /* 1883 * Use this lookup routine when performing relocations early during boot. 1884 * The generic lookup routine depends on kobj, which is not initialized 1885 * at that point. 1886 */ 1887 static int 1888 elf_lookup_ifunc(linker_file_t lf, Elf_Size symidx, int deps __unused, 1889 Elf_Addr *res) 1890 { 1891 elf_file_t ef; 1892 const Elf_Sym *symp; 1893 caddr_t val; 1894 1895 ef = (elf_file_t)lf; 1896 symp = ef->symtab + symidx; 1897 if (ELF_ST_TYPE(symp->st_info) == STT_GNU_IFUNC) { 1898 val = (caddr_t)ef->address + symp->st_value; 1899 *res = ((Elf_Addr (*)(void))val)(); 1900 return (0); 1901 } 1902 return (ENOENT); 1903 } 1904 1905 void 1906 link_elf_ireloc(caddr_t kmdp) 1907 { 1908 struct elf_file eff; 1909 elf_file_t ef; 1910 1911 ef = &eff; 1912 1913 bzero_early(ef, sizeof(*ef)); 1914 1915 ef->modptr = kmdp; 1916 ef->dynamic = (Elf_Dyn *)&_DYNAMIC; 1917 1918 #ifdef RELOCATABLE_KERNEL 1919 ef->address = (caddr_t) (__startkernel - KERNBASE); 1920 #else 1921 ef->address = 0; 1922 #endif 1923 parse_dynamic(ef); 1924 1925 link_elf_preload_parse_symbols(ef); 1926 relocate_file1(ef, elf_lookup_ifunc, elf_reloc, true); 1927 } 1928 1929 #if defined(__aarch64__) || defined(__amd64__) 1930 void 1931 link_elf_late_ireloc(void) 1932 { 1933 elf_file_t ef; 1934 1935 KASSERT(linker_kernel_file != NULL, 1936 ("link_elf_late_ireloc: No kernel linker file found")); 1937 ef = (elf_file_t)linker_kernel_file; 1938 1939 relocate_file1(ef, elf_lookup_ifunc, elf_reloc_late, true); 1940 } 1941 #endif 1942 #endif
Cache object: a7dfe85c68de4a39490e468e089785a8
[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]